The widespread use of digital processing technology has found its way into a variety of equipment and, in some form, into most industries. In many applications involving communicating different types of information, communication systems have been configured to transmit information from each type of information source over various communications media.
In some multimedia application environments, for example, communication systems permit several data sources to transmit data over a communication channel. In such an environment, a communication system typically processes certain types of data from each of the several data sources and presents this processed data to communication channel transmission equipment, such as a modem, in an orderly fashion.
The communication system formats the processed data for transmission using operational modes known as capabilities. Each type of data may be formatted using any of a variety of capabilities. For example, video data may be transmitted using capabilities supporting the H.261 and H.263 standards specified by the Telecommunication Standardization Sector of the International Telecommunication Union (ITU-T). When a connection is first established between communication systems operating in such an environment, each system typically broadcasts to the other its valid operating modes in order to establish a set of capabilities for use during the session. The systems then select a set of capabilities that are ideally compatible with each system.
Selecting the capabilities is complicated by certain constraints on simultaneous use of capabilities. Due to system limitations, such as memory constraints, not all capabilities can be simultaneously operated. Rather, many communication systems can use the capabilities only in certain combinations. When establishing the connection, each system typically transmits its constraints to the other, which takes these constraints into consideration in selecting the capabilities for use during the session.
In addition, many communication systems lack uniformity in the capabilities they support. As a result, it is often difficult, if not impossible, to select capabilities that the communication systems involved in the session support.